The graph shows how the magnification m produced by a convex thin lens varies with image distance v. What was the focal length of the used?

Question

The graph shows how the magnification m produced by a convex thin lens varies with image distance v. What was the focal length of the used? (A) (b/c) (B) (b/c a) (C) (b c/a) (D) (c/b)

Tardigrade Admin · Accepted Answer

For a lens m=(f-v/f)=-(1/f) v+1 Comparing it with y=m x+c Slope =m=-(1/f) From graph, slope of the line =(b/c) Hence -(1/f)=(b/c) ⇒ |f|=(c/b)

Q. The graph shows how the magnification $m$ produced by a convex thin lens varies with image distance $v$ . What was the focal length of the used?

$\frac{b}{c}$

$\frac{b}{c a}$

$\frac{b c}{a}$

$\frac{c}{b}$

For a lens $m = \frac{f - v}{f} = - \frac{1}{f} v + 1$
Comparing it with $y = m x + c$
Slope $= m = - \frac{1}{f}$
From graph, slope of the line $= \frac{b}{c}$
Hence $- \frac{1}{f} = \frac{b}{c}$
$\Rightarrow ∣ f ∣ = \frac{c}{b}$

Q. The graph shows how the magnification m produced by a convex thin lens varies with image distance v. What was the focal length of the used?

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cab​

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